Today, a huge amount of personal cards is in practical use, with an increasing focus on applications requiring higher security. RFID technology was implemented as a comfortable interface for the user and world-wide standardized about one decade ago in the ISO/IEC14443 Proximity Standard. This standard, as well as all other standards in the field of RFID are considered to be well-known to the person skilled in the art. RFID technology enabled electronic passports, contactless credit cards (E-banking), access control or public transport ticketing as successful solutions being part of our daily life. The typical format of such cards is ID-1, specified in the ISO/IEC7810 standard.
A new trend is visible wherein RFID technology is being used for payment applications. In such applications contactless stickers with ISO/IEC14443 smartcard transponder chips are sticked to mobile phones, for example. Mobile Phones may have cases made of plastic, containing metal parts, or consist of metal, and may have different sizes. A typical transponder card attached to a metal plate will not operate properly, because the magnetic flux passing through the antenna coil will produce eddy currents in the metal, and these will produce an opposite H-field, which practically cancels out completely the Reader field. Thus, the contactless transponder gets no energy for operation. A ferrite foil in-between transponder loop antenna and metal case will allow a part of the magnetic flux to pass through the foil, and not contribute to the eddy currents. The result is that some H-field remains to power the transponder and allow (limited) operation. Such contactless systems operate with resonance to increase induced voltage. The antenna design must meet the criterion that resonance frequency is close to the operating carrier frequency, to have most energy. Loop antennas with ferrite will be detuned in different way by the presence of metal or plastic (˜3 MHz for a practical case).
A problem of the known RFID transponder is that it is no longer applicable to any surface material once it has been optimized for one surface material (for example metal). Such optimization is done in the manufacturing stage of the RFID transponder.